Israel Shifts to Winter Time; Study Links Season to Cognitive Performance

Israel and other countries will transition to winter time on the night of October 30, moving clocks back one hour. Beyond the known effects of daylight on mood, a new question arises about whether cognitive functions like memory and thinking also change seasonally. A study published in PLOS Medicine, analyzing data from 3,353 adults in the U.S., France, and Canada, identified a consistent seasonal pattern: cognitive performance was better in summer and lower in winter. Researchers estimated the difference between peak and trough performance could be equivalent to the cognitive impact of approximately 4.8 years of aging. However, the study was observational and focused on adults, thus it does not definitively prove that winter itself impairs memory or that the shift to winter time causes cognitive decline.

Eti Aniel, a researcher in brain and memory at Bar-Ilan University, clarified that the study does not suggest the brain enters a "winter mode" upon the clock change. He explained that the measured differences represent population averages and may not be noticeable to individuals. Aniel noted that the findings indicate cognitive performance is not constant year-round and that the brain is sensitive to environmental rhythms. Seasonal changes in light, sleep, mood, physical activity, and routine all occur simultaneously, making it difficult in observational research to isolate a single cause for cognitive shifts.

Daylight is a significant factor, as it is a primary regulator of the biological clock, influencing sleep-wake cycles, melatonin secretion, and alertness. While the shift to winter time doesn't shorten the day, it alters the alignment between clock time and natural light. For some, this can cause temporary sleep disturbances, which in turn can affect concentration, learning, and memory recall. Aniel suggested that difficulties might stem from the initial encoding of information, where attention is crucial. "When we are tired, distracted, or preoccupied with our mood, the brain often encodes information less efficiently and processes it less deeply," he stated. He also highlighted sleep's role in consolidating memories, noting that disrupted sleep can impair this process, leading to a feeling of forgetfulness even if information was never efficiently stored.

The article also touched upon Vitamin D, citing a study that found a link between low levels and faster decline in episodic memory and executive functions in adults. However, this was also an observational study, preventing definitive conclusions about causality. Aniel advised against automatic supplementation for memory protection, emphasizing that the observed correlation could work in reverse and that controlled trials on supplements have not shown consistent cognitive improvements in the general population. He recommended consulting a doctor to check for a genuine deficiency.

Ultimately, the transition to winter time does not necessarily mean memory impairment. It does, however, underscore the connection between brain function and factors like light, sleep, routine, and psychological state. If individuals feel slower, more distracted, or forgetful during winter, the cause may lie in the conditions under which memory is asked to perform, rather than in the memory itself.